Heretofore, compositions comprising ferromagnetic materials have provided conductive or inductive adhesives, films, and inks. However, these compositions have thus far comprised solvents and other volatile organic compounds (VOCs) which rapidly volatilize to dry the adhesive, film, or ink and which present health and environmental hazards.
More recently, liquid epoxy coatings comprising ferromagnetic materials and adhesive resins have been proposed. Such coatings may be cured through induction heating of the ferromagnetic materials. However, adhesive resin coating materials are very difficult to handle, as they tend to irreparably foul the equipment used to apply them unless they contain high amounts of VOCs. Further, these coatings are not free of hazardous VOC's, especially when formulated as low solids lacquers to reduce viscosity. Still further, the overspray from any liquid coatings can be reclaimed or recycled only at costs greater than the coating materials themselves.
WO-01/51568 A1, to UV Specialties, discloses ultraviolet light (UV) curable ferromagnetic compositions used in the screen printing of capacitors and inductors. The compositions contain conductive/magnetic powder, UV curing resins, such as acrylated oligomers, and less than 5 weight % of VOCs. However, the UV curable compositions provide only conductive screen printable coatings having a relatively high ferromagnetic material content. Further, such low VOC compositions are not tailored to meet the flexible weatherability, durability and chemical resistance needs provided in protective coatings for durable goods and for interior and exterior architectural use. Still further, such compositions do not provide satisfactory appearance properties for use in decorative coatings. Finally, the overspray from any liquid coating compositions can be reclaimed or recycled only at costs greater than the coating materials themselves.
In accordance with the present invention, the inventors have discovered coating compositions that are free of VOCs, that are fully recyclable, and which provide coatings having excellent functional and appearance properties when cured via magnetic induction.